Vehicle intermittently down shifts (feels like Torque converter clutch disengageing)
At highway speeds. Transmission was replaced issue still remains. FORD/Mecury dealers seem lost. Any Ideas No trouble codes.

Thank you

I have a 2000 Ford Taurus, with the 3.0 L Duratec engine and AX4N transaxle. I was somewhat disappointed in how the transaxle performed with regular Mercon V ATF. When I dropped and cleaned the pan, changed the filter, and refilled with Amsoil Universal Synthetic ATF the performance improved dramatically. No more odd downshifts and performance and mileage has improved. Even my wife can tell the dramatic improvement in shift quality. People make a mistake, in my opinion, not using state-of-the-art synthetic lubricants in their vehicles. You can't afford not to use them. Install a B&M transmission drain pan plug to facilitate changing ATF more often.

Synthetic ATF is the key to getting maximum life and performance from your ATX. They run much cooler and stay super clean inside. Today's electro-mechanical transaxles hate dirt, varnish, and sludge. Change fluid and filter every 30,000 miles. It was amazing how much crud formed in the bottom of the pan, when it was first changed at 29,000 miles.

ATXs are the weak link in modern-day FWD cars. The situation is getting worse, not better. It's particularly bad on imported cars, where it's best to stick with manual transmissions. Import manual transmissions, however, are very good.